You can connect three and it will work.
But if you try to use more than two concurrently then the performance will drop off rapidly.
The technololgy has exactly the same performace issues as the old (BNC connected) 'thin wire' ethernet which has now almost dissapeared from use.
Line One:- Zen - DrayTek Vigor 2600VG
Line Two:- EntaNet (Aquiss) - DrayTek Vigor 2600